Polyamide and polyester fibers have poor resistance to oxidizing agents, particularly to sodium hypochlorite. Polyester fibers and polyamide fibers, including all grades of nylon, lose strength after being in contact with sodium hypochlorite solution for a few hours.
In the manufacture of paper from cellulosic fiber wood pulp, the pulp is subjected to bleaching to increase the whiteness or brightness of the paper subsequently produced from the pulp. In this bleaching operation the pulp is exposed to oxidizing agents such as hydrogen peroxide and sodium hypochlorite and is thereafter conveyed to a paper-making operation. In these procedures the pulp is conveyed on a porous, self-supporting carrier sheet in the form of an elongate, continuous belt, and this carrier sheet, referred to in the paper-making art as a felt, is exposed to the oxidizing or bleaching chemical.
The exposure of the carrier sheet to the oxidizing or bleaching chemical substantially lowers the useful life of the felt.
These felts which typically may be 45 to 135 meters, in length, 7 meters wide and 3 to 5 mm thick are expensive typically costing several thousand dollars. The exposure of the felts to the bleaching or oxidizing agents, so degrades the felts that their useful life is not more than 40 days in continuous operation and frequently as short as 20 days. Various solutions have been tried to overcome this problem. One is to treat the felt with chlororesorcinol or chlororesorcinol formaldehyde, or a combination of chlororesorcinol and acid dyes. This improves the resistance of the felt to chlorine to a certain extent, but it does not have a useful effect against hydrogen peroxide. Another solution that has been tried is to apply melamine formaldehyde resin to the felt; however, this treatment makes the felt very stiff.